Please note that the “Workflow Service EndPoint URL” can be found in your SharePoint Server’s IIS Manager:

Please pay a close attention to the protocol your Workflow Service is using. By mistake I put http:// instead of https:// and I was getting error below:

Register-SPWorkflowService : The underlying connection was closed: An unexpected error occurred on a receive.

After running the Powershell command you would need to go to your Central Admin and check the “Workflow Services Application” under “Manage Service Applications”. The Workflow Service Status should read “Workflow is connected”. Once the workflow is connected you should be able to see the “SharePoint 2013 Workflow” in your SharePoint Designer.